PROGRESS
REPORTS
2016
FISH DIVISION
Oregon Department of Fish and Wildlife
Clackamas River Bull Trout Reintroduction Project:
Monitoring bull trout with census redd counts and PIT tag technology, 2011-2016
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Clackamas River Bull Trout Reintroduction Project:
Monitoring bull trout with census redd counts and
PIT tag technology, 2011-2016
Steve Starcevich, ODFW Native Fish Investigations Program
Corvallis Research Lab, December, 2016
Abstract
Bull trout were extirpated from the Clackamas River basin by the 1960s. A reintroduction
feasibility assessment and an implementation plan were completed in 2007 and 2011, respectively,
with the goal of establishing a self-sustaining population of 300-500 adults in the Clackamas River
basin. Phase one of the project (2011-2016) involved translocating 2,868 bull trout (80% as age-1
and 2) from the Metolius River basin, tagging each with a passive integrated transponder (PIT tag),
releasing them in the upper Clackamas River basin, and monitoring them using a variety of
methods. Monitoring methods included census redd counts and detection of PIT-tagged bull trout
at a PIT detection site in Pinhead Creek. The number of redds observed and adult PIT-tagged bull
trout (defined as age-5 and older) detected have steadily increased from 18 redds and 15 adults in
2013 to 68 redds and 72 adults in 2016. There was a strong linear relationship between the annual
redd count and the number of adults detected in Pinhead Creek, suggesting that redd counts may
be useful in tracking trend in adult abundance. In 2016, adults detected in Pinhead Creek were
translocated mainly at age-1 and 2 (i.e., 70-210 mm), released at locations both in Pinhead Creek
and the Clackamas River, and spent a median of 26 d in Pinhead Creek during the spawning period.
The second phase of the project begins in 2017 and entails continued monitoring of progress
toward the reintroduction goal, at least in part through census redd surveys and the use of PIT tag
technology, of producing naturally-reproducing, self-sustaining population of bull trout in the
Clackamas River basin.
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Introduction
Bull trout (Salvelinus confluentus) were extirpated from the Clackamas River basin by the 1960s.
A feasibility assessment (Shively et al. 2007) and an implementation plan (US Fish and Wildlife
Service [USFWS] 2011) for bull trout reintroduction were completed with the goal of establishing
a self-sustaining population of 300-500 adult in Clackamas River basin. The reintroduction was
divided into three phases of approximately 6-7 years each (USFWS 2011). The first phase was
from 2011-2016 and involved translocating 2,868 bull trout from the Metolius River basin (Table
1), giving each one a unique passive integrated transponder (PIT tag), releasing them at various
locations and lifestages (80% of which were between 70-250 mm total length) in the upper
Clackamas River basin, and then monitoring them using radio telemetry, PIT tags, electrofishing,
and redd surveys. The second phase begins in 2017 and entails continued monitoring of progress
toward the reintroduction goal, at least in part through census redd surveys and the use of PIT tag
technology.
Redd surveys from 2011 to 2014 were conducted by an ad hoc multi-agency group of observers.
In 2015 and 2016, census redd surveys were conducted by a crew of five experienced observers
from the Oregon Department of Fish and Wildlife (ODFW), with additional help from other
agencies and volunteers. In 2015, a long interval (44 d) between censuses may have increased
uncertainty and observer error in identifying new bull trout redds and discerning them from redds
constructed during a previous season or by other fall-spawning fish species such as Chinook
salmon (Oncorhynchus tshawytscha) or coho salmon (O. kisutch). In 2016, the objectives were to
1) evaluate the effectiveness of a two-week interval between each census conducted throughout
the potential spawning period, 2) use thermographs to refine the sampling frame and focus surveys
in thermal habitat suitable for bull trout spawning, 3) examine relationships between redd counts
and PIT-tagged bull trout detected in the Pinhead Creek watershed, and 4) characterize the spatial
and temporal distribution of salmon spawning.
Methods
Census redd surveys
A five-person crew conducted census redd surveys in all potential bull trout spawning habitat in
the upper Clackamas River and major tributary basins (Figure 1). Census surveys were generally
completed every two weeks (Table 2). The first census survey was conducted in mid-August, prior
to the putative start of bull trout and Chinook salmon spawning. This survey was used to
familiarize the field crew with bull trout redd identification by analyzing characteristics of old
redds from a previous season (i.e., redds constructed prior to August) and flagging areas that could
be mistaken for new redds. A new bull trout redd was identified by its pocket-mound structure,
smaller gravel size relative to substrate in Chinook salmon redds, and the contrast of brighter
disturbed gravel relative to darker surrounding substrate matrix. Chinook and coho salmon redds
were distinguished by larger dimensions and substrate size and by identifying the species of adult
salmon occupying a redd. The crew flagged new bull trout redds and recorded the following data:
GPS location, maximum length and width, species and number of adults occupying redd, and brief
descriptions of observer certainty.
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Table 1. PIT-tagged bull trout translocated from the Metolius River basin to the Clackamas River basin in
the first phase of the reintroduction project. Lifestages were defined by the size classes 70-250 mm
(juvenile), 251-450 mm (subadult), 451-650 mm (adult).
Lifestage Date
Year Location Juvenile Subadult Adult Min Max
2011 Clackamas River 0 0 11 30-Jun 30-Jun
Clackamas River 1 0 14 3 30-Jun 30-Jun
Clackamas River 2 0 11 21 30-Jun 15-Jul
Last Creek 42 0 0 30-Jun 15-Jul
Pinhead Creek 16 0 0 21-Jul 21-Jul
2011 Subtotal 58 25 35
2012 Clackamas River 1 0 9 1 14-Jun 14-Jun
Clackamas River 2 2 34 16 14-Jun 12-Jul
Last Creek 151 0 0 3-May 28-Jun
Pinhead Creek 364 0 0 10-May 31-May
2012 Subtotal 517 43 17
2013 Clackamas River 3 30 3 6-Jun 13-Jun
Clackamas River 1 0 60 5 6-Jun 27-Jun
Last Creek 338 0 0 11-Apr 27-Jun
Pinhead Creek 283 0 0 2-May 30-May
2013 Subtotal 624 90 8
2014 Berry Creek 296 0 0 24-Apr 29-May
Clackamas River 1 26 45 7 5-Jun 25-Jun
2014 Subtotal 322 45 7
2015 Berry Creek 287 1 0 10-Apr 5-Jun
Clackamas River 1 13 73 7 15-May 5-Jun
2015 Subtotal 300 74 7
2016 Clackamas River 1 95 94 6 20-May 13-Jun
Clackamas River 5 501 0 0 8-Apr 13-May
2016 Subtotal 596 94 6
Total 2417 371 80
Grand total 2868
Salmon redds generally were not treated individually, except in Pinhead Creek and Last Creek,
where they were treated like bull trout redds. Elsewhere, the crew usually recorded the number of
salmon redds tallied over 100-300 m survey sections and a GPS location for each section mid-
point.
Bull trout and salmon redd data were entered in an Access database that contains data from
previous bull trout spawning surveys in the upper Clackamas River basin. Each year spawning
surveyors recorded observations of some bull trout redds described as “potential”, “possible”,
“likely”, “test dig?” or some other variant registering uncertainty in their observations; these
descriptions were included in the database. In 2015 and 2016, observers were trained to include a
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Figure 1. Survey extent, potential natural fish barriers, and salmon and bull trout redds observed during
census redd surveys in the upper Clackamas River basin. Each bull trout and coho salmon marker represents
a single observed redd. Chinook salmon redds were not individually georeferenced, thus an individual
Chinook marker may represent multiple redds (range, 1-30 redds) counted over a survey extent (range, 100-
200m). Secondary channels are not shown and redd markers have not been snapped to the stream line.
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Table 2. Census survey schedule and reaches and the number of bull trout redds counted in each census.
Some reaches were not surveyed (NS) in each census.
